The present invention relates to a governor or an internal combustion engine especially for an industrial vehicle such as a forklift truck.
There is shown in FIG. 16 a known carburetor assembly in which a governor device 54 for controlling the maximum rotational speed (NMR) of an engine in a no-load condition is interposed between a carburetor 52 and an intake manifold 63. A governor valve 55 of the governor 54 is rotatably supported on a shaft 56 in an air/fuel mixture supply passage 60 so as to control the flow through the air/fuel mixture supply passage 60. The governor valve 55 is normally biased to its fully open position by a spring (not shown).
A piston 57 is connected through an operating rod 58 to the governor valve 55. The piston 57 is reciprocatively disposed in a cylinder chamber 59 partitioning the cylinder chamber 59 into a first chamber 59a and a second chamber 59b. The first chamber 59a is placed in communication through a communication passage 61 with the air/fuel mixture supply passage 60 at a position downstream of the throttle valve 53 of the carburetor 52. The second chamber 59b is placed in communication through a hose 62 with an air filter 51.
In operation, when the engine is driven, the piston 57 is reciprocated in response to a change in pressure in the air/fuel mixture supply passage 60 to thereby control the position of the governor valve 55 and control the quantity of the air/fuel mixture being supplied to the engine, thus controlling the rotational speed of the engine.
FIG. 17 is a graph showing the output characteristic of the engine with the above prior art governor device compared with the output characteristic of an engine without such governor device.
As apparent from FIG. 17, the maximum output of the engine with the air governor device is lower by about 15% to 30% (shown by H in FIG. 17) than that of the engine with no air governor device. This is considered to be due to the fact that the presence of the governor valve 55 in the air/fuel mixture supply passage 60 causes flow resistance. That is, the engine with the governor device in the prior art cannot derive full power.